When one is sick, the events of that sickness is burnt into one's memory vividly. What happens at what time, and what lead to what event, and so on and so forth. It also brings forward the mood to plan for a future where health is plenty. Planning for the future is always a gamble, a big one, but when one is sick, everything is put into perspective. When one is sick, health seems like a good opportunity to do the things one never did before out of apathy.